Liquid-gaseous fuel burner



1965 E. M. RUDZKI ETAL LIQUID-'GASEQUS FUEL BURNER Filed Sept. 4, 1963My a 2; INVENTORS Eugene M Rudz/r/ BY Richard J Reinhold Bradford APease United States Patent 3,213,918 LIQUID-GASEOUS FUEL BURNER EugeneM. Rudzki and Richard J. Reinhold, Bethlehem, and Bradford K. Pease,Allentown, Pa., assignors, by mesne assignments, to Bethlehem SteelCorporation, a

corporation of Delaware Filed Sept. 4, 1963, Ser. No. 306,510 Claims.(Cl. 15811) This invention relates to an improved combinationliquid-gaseous fuel burner particularly suited for intermittentoperation in a metallurgical furnace. More specifically it is directedto a burner in which liquid fuel is atomized by low pressure gas, i.e.gas at a pressure no greater than 15 p.s.i.g., under varying operatingconditions, and wherein the liquid fuel nozzle is continuously purged bya fluid medium during the idle portion of an operating cycle.

In the metallurgical industry various types of fuels such as oil, tar orgas are used to heat furnaces. In some instances a combination of thesefuels are used, as for example in the large open hearth furnacesutilized to make steel. In a conventional open hearth burner firing acombination of gaseous and liquid fuel, both fuels pass through thewater cooled burner casing in separate tubes and become mixed upon theirdischarge from the burner. The liquid fuel is atomized by steam, at therear of the burner, before it passes through its tube into the furnace.However, the use of atomizing steam reduces the flame temperature andincreases the volume of combustion products passing through the checkersand lines.

It is an object of the present invention to provide a burner whereinliquid fuel is atomized, without the use of steam, by low pressure gas.

Another object is to provide an improved liquid-gaseous fuel burnerwhich will produce a higher flame temperature than is produced by thistype burner at the present time.

Another object is to provide a liquid-gaseous fuel burner which, ascompared to conventional burners, will decrease the volume of combustionproducts passing through a furnace operating under similar conditions.

Another object is to provide a liquid-gaseous fuel burner that utilizesa pressure nozzle for initial atomization of the liquid fuel prior toits atomization by the gas.

It is a further object to provide a liquid-gaseous fuel burner whereinthere is a continuous purge of the liquid fuel nozzle during the idleperiods of an operating cycle to prevent the accumulation of foreignmatter in the nozzle orifice. Other objects and advantages of thisinvention will be apparent from the following specification and theaccompanying drawings, in which FIG. 1 is a side elevation, partly crosssectional, of the improved oil burner of the present invention;

FIG. 2 is a sectional view of the discharge end of the burner; and

FIG. 3 is a view of the back end of the burner.

For purposes of illustration this invention will be describe-d withparticular relation to open hearth burners adapted to burn a combinationof liquid and gaseous fuel, but it is not necessarily limited thereto.Those familiar with steelmaking operations know that a single burner isused at each end of an open hearth furnace, and, in heating the charge,the burners are fired alternately. Some liquid gaseous fuel burners havea plurality of ports in the liquid nozzle which all-ow the burner toremain in service when some of the ports become obstructed; otherburners of this type require high pressure gas to provide the desireddegree of atomization of the liquid fuel. Our invention utilizes lowpressure gas and provides a novel means of automatically andcontinuously purging the liquid fuel nozzle of a liquid-gaseous burnerduring the idle portion of an operating cycle. By purging the liquid 3213,918 Patented Oct. 26, 1965 fuel nozzle immediately after the fuelhas been shut off, the accumulation therein of carbonized residual fuelis prevented. By continuing the purging for the entire period of timethe burner is inactive, the pressure and cooling effect of the purgemedium prevent the adherence of slag and other foreign matter to thenozzle. The purge medium is always available at the discharge end of theburner but only flows through the nozzle when the liquid fuel pressurewithin the nozzle drops below the pressure of the purge medium.

Referring now to the drawings in detail, the invention is illustrated asembodied in a pressure responsive gas atomizer burner 10. The portion ofthe burner which projects into the furnace is enclosed by a casing 11which forms a chamber 12 adapted to have a suitable coolant circulatedtherethrough. A gaseous fuel pipe 13 extends longitudinally throughcasing 11 and projects beyond the back end of said casing, as shown inFIG. 1. The front end of gaseous fuel pipe 13 has a forwardly andinwardly inclined inner surface 14 which terminates in a circular axialorifice 15. Atomizing gas flows into fuel pipe 13 through inletconnection 16, and the pressure of the gas within the fuel pipe 13 istransmitted to a cont-roller, not shown, on the furnace panel board,through pressure tap 17 and pressure impulse line .18. Joined to therear end of fuel pipe 13 by means of union 19, is back plate assembly20, as shown in FIG. 3.

Back plate assembly 20 comprises a sleeve 21, of slightly smalleroutside diameter than the inside diameter of fuel pipe 13, connected tocasing 22, and back plate 23, which .is bolted to the flanged back endof casing 22. The front end of casing 22 is threaded to receive one halfof union 19. The other half of union 19 is screwed to the threaded backend of casing 13. Axially located in back plate 23 is seal assembly 24with O-ring seals 25. A narrow slot 26 is machined in the forwardsection of sleeve 21 for a purpose to be hereinafter more fullydescribed. A positioner 27 is mounted on back plate assembly 20 by meansof bracket 28. Pos-itioner 27 is remotely connected by impulse line 29to the furnace panel board, from which the operation of the burner iscontrolled.

Extending longitudinally within fuel pipe 13 is liquid fuel tube 30. Therear portion of fuel tube 30 extends through seal assembly 24 of backplate 23 and beyond the rear end of gaseous fuel pipe 13. Liquid fuelnozzle 31 with insert 32 is connected to the forward end of the liquidfuel tube. Between the liquid fuel tube 30 and liquid nozzle 31 areinterposed check valve 33 and suitable fitings 34, all axially assembledto allow the continuous unobstructed passage of liquid fuel, in aforward direction, through the assembly. There is a single axial orifice35 in the forward end of nozzle 31, and in its side wall, closelyadjacent orifice 35, is purge opening 36. Guide fins 37, spaced apart,on the rear of nozzle 31 and guides 38 mounted on fuel tube 30 insurethat the fuel tube moves axially within the fuel pipe 13 and that thenozzle 31 cooperates, in a manner hereinafter more fully described, withthe inclined inner surface .14 of fuel pipe 13 to form a variableannular opening 39 which terminates in orifice 15. Fuel tube 30 is madein sections joined by fittings 40 to facilitate assembly anddisassembly. A backward motion stop 41 is mounted on fuel tube 30,within fuel pipe .13, near its back end. The L-shaped extension of stop41 moves within previously mentioned slot 26 of sleeve 21 of back platevassembly 20 and prevents fuel tube 30 from moving to the rear more thana limited distance. Outside the back end of fuel pipe 13, a forwardmotion stop 42 is mounted on fuel tube 30 and prevents it from movingforward more than a limited distance. Tube 30, at its back end, isconnected to one branch of fit-ting 43. Another branch of fitting 43 isconnected, by means of a flexible tube 44, to an oil supply system, notshown. The

3 third branch of fitting 43 is coupled to shaft 45 of positioner 27.

Also disposed within gaseous fuel pipe 13 is purge c-onduit 46. -At itsforward end, this conduit is connected to nozzle 31 at purge opening 36.Just to the rear of this connection, check valve 47 is axially mountedin conduit 46 in a manner to allow the unobstructed flow of the purgemedium through said conduit in a forward direction but to prevent theflow, in the opposite direction, of liquid fuel into said conduit. Purgeconduit 46 is formed in sections, joined by fittings 48 and 49, tofacilitate maintenance. In addition to being connected to fuel nozzle 31on the forward end of fuel tube 30, purge conduit 46 is fastened toliquid fuel tube 30 by clamps 50 so that tube 30 and conduit 46 move asa unit. A portion of conduit 46, near its back end, is formed into acoil 51 which encircles fuel tube 3i Coil 51 acts as an expansion meanswhich prevents the failure of conduit 46 due to thermal stresses andpermits it to move, without breaking, in conjunction with fuel tube 30.The back end of coil 51 of conduit 46 is joined to fitting 52, in backplate 23, which in turn is connected by mean-s of pipe 53 to a source,not shown, of purge medium.

The burner of this invention has the liquid fuel introducedconcentrically within the gas stream as these fuels are discharged fromtheir respective passageways at the forward end of the assembly. Inaddition to the atomization created by the pressure atomizing fuelnozzle 31, impingement of the gas upon the liquid further atomizes it.The degree of atomization caused by the gas is dependent upon itsvelocity, and the pressure and velocity of the gas are sustained at amaximum rate by maintaining the annular opening 39 at the minimumcross-sectional area required to pass the desired amount of gas.

The control of the burner, including the regulation of the fuel rate,takes place at the furnace instrument panel. The flow rate of liquidfuel fired during an open hearth heat is generally maintained constant,and any changes in the firing rate, made in accordance with the firingschedule, are accomplished by varying the gas flow. The pressure andflow of fuel through the burner is adjusted by controllers on thefurnace panel board. The gas pressure controller is connected by impulseline 18 to pressure tap 17, on burner fuel pipe 13, and by impulse line29 to positioner 27. Variations in pressure within fuel pipe .13 aretransmitted to the gas pressure controller on the panel board and thenrelayed to the positioner 27. The positioner compensates for thesevariations .in pressure of the gas by axially displacing liquid nozzle31, to which it is remotely connected. The displacement of the liquidnozzle varies the cross-sectional area of annular opening 39 andmaintains a constant and maximum gas velocity through said openingindependent of the flow rate of gas into fuel pipe 13.

The alternate firing of the furnace burners is also regulated at theinstrument panel and usually operates on a fixed time cycle. When thefuel to a burner is shut oif, the pressure within the liquid fuel tube30 immediately drops. When this pressure drops below the pressure of thepurge medium in conduit 46, the purge medium, always available withinsaid conduit, opens check valve 47 in said conduit, and the purge mediumflows through nozzle 31 and out through orifice 35. Any residual fuelremaining in the nozzle chamber is evacuated by the purge medium, andcoking or charring of residual liquid fuel within the nozzle isprevented. Check valve 33 is automatically closed by the pressure of thepurge medium which is thus prevented from entering fuel tube 30. Thepurge medium flows continuously through the fuel nozzle during the timethe burner is idle, and the pressure and cooling effect of the mediumprevent slag and other foreign matter from being deposited on thenozzle.

When the furnace reverses and the inactive burner, the nozzle of whichwas continuously purged, goes into service, the liquid fuel, at a higherpressure than the purge medium, opens check valve 33 and again flowsthrough tube 30, check valve 33, nozzle 31, and orifice 35. Check valve47 in the purge conduit closes and prevents the liquid fuel from flowingthrough that line.

The backward motion stop 41 and the forward motion stop 42 mounted onfuel tube 30 operate as stops of this nature normally function and, byrestricting movement of the fuel tube and purge conduit, prevent the gasfrom being shut off completely under adverse conditions and prevent theburner from being damaged.

In the specific embodiment of this invention as described, the liquidfuel nozzle 31 was designed to pass 150 GPH of blended pitch at apressure of 150 p.s.i.g. through orifice 35, which was 0.014" indiameter. Steam at a pressure of about 110 p.s.i.g. was utilized as thepurge medium, and the pressure of the gas was maintained atapproximately 14 p.s.i.g. The liquid nozzle 31 illustrated in FIGURES 1and 2 has an insert 32 which produces a full cone spray pattern, andwhile various nozzles may be utilized, the pattern of atomized dropletsproduced by this type nozzle was found to be most advantageous for ourservice. The positioner 27 was a direct acting positive displacementtype, but other positioners may be utilized.

In the burner described above, the purge steam consumption variedbetween 30 and 40 pounds per hour as compared to the 1050 pounds ofsteam per hour previously consumed, under similar conditions, by burnersutilizing conventional steam atomization of liquid fuel. In plants wherethere is a limited amount of steam available for all purposes, thereduction in steam consumption realized by the use of our burner is ofconsiderable importance. Other benefits realized from the use of thespecified burner are flame temperatures approximately F. higher thanthose produced by a conventional burner, greater availability of hightemperature heat, and a decrease in the volume of combustion products ofabout 4%.

Although certain novel features of our invention have been shown anddescribed, it will be understood that changes and modifications may bemade without departing from the spirit of the invention or the scope ofthe appended claims.

We claim:

1. A liquid fuel burner adapted for intermittent operation in a furnacecomprising, within said burner:

(a) a liquid-fuel-supply tube terminating at its outer end in arestricted orifice,

(b) a first check valve in said liquid-fuel-supply tube located to therear of and closely adjacent to said tube orifice and arranged to permitforward flow of liquid fuel through said supply tube and check valve andout of said tube orifice and to prevent back flow of fluid through saidfirst check valve,

(c) a purging-medium-supply conduit communicating with saidliquid-fuel-supply tube between said tube orifice and said first checkvalve,

(d) a second check valve in said purging-mediumsupply conduit closelyadjacent to said tube orifice and arranged to permit forward flow ofpurging medium through said purging-medium-supply conduit and secondcheck valve and out of said tube orifice and to prevent back flow offluid through said second check valve,

(e) a pipe surrounding said liquid-fuel-supply tube, said first checkvalve, said purging-medium-supply conduit, and said second check valve,

(f) means to intermittently supply liquid fuel to sa1dliquid-fuel-supply tube for ejection through the tube orifice therein,and

(g) means to supply purging medium to sa1d purglngmedium-supply conduitfor ejection through the tube orifice in said liquid-fuel-supply tubeduring periods when liquid fuel is not being ejected therethrough,

2. A liquid-gaseous fuel burner adapted for intermittent operation in afurnace comprising, within said burner:

( a) a liquid-fuel-supply tube terminating at its outer end in arestricted orifice,

(b) a first check valve in said liquid-fuel-supply tube located to therear of and closely adjacent to said tube orifice and arranged to permitforward flow of liquid fuel through said supply tube and check valve andout of said tube orifice and to prevent back flow of fluid through saidfirst check valve,

(c) a purging-medium-supply conduit communicating with saidliquid-fuel-supply tube between said tube orifice and said first checkvalve,

(d) a second check valve in said purging-mediumsupply conduit closelyadjacent to said tube orifice and arranged to permit forward flow ofpurging medium through said purging-medium-supply conduit and secondcheck valve and out of said tube orifice and to prevent back flow offluid through said second check valve,

(e) an atomizing-gas-supply pipe surrounding said liquid-fuel-supplytube, said first check valve, said purging-lrnedium-supply conduit, andsaid, second check valve, said atomizing-gas-supply pipe terminating atits outer end in an orifice adjacent to said liquid-fuel-supply tubeorifice,

(f) means to intermittently supply liquid fuel to saidliquid-fuel-supply tube for ejection through the tube orifice therein,

(g) means to supply atomizing gas to said atomizinggas-supply pipe, and

(h) means to supply purging medium to said purgingmedium-supply conduitfor ejection through the tube orifice in said liquid-fuel-supply tubeduring periods when liquid fuel is not being ejected therethrough.

3. A liquid-gaseous fuel burner adapted for intermittent operation in afurnace comprising (a) a liquid-fuel-supply tube terminating at itsouter end in a restricted orifice,

(b) a first check valve in said liquid-fuel-supply tube located to therear of and closely adjacent to said tube orifice and arranged to permitforward flow of liquid fuel through said supply tube and check valve andout of said tube orifice and to prevent back flow of fluid through saidfirst check valve,

(0) a purging-steam-supply conduit communicating with saidliquid-fuel-supply tube between said tube orifice and said first checkvalve,

(d) a second check valve in said purging-steam-supply conduit closelyadjacent to said tube orifice and arranged to permit forward flow ofpurging steam through said purging-steam-supply conduit and second checkvalve and out of said tube orifice and to prevent back flow of fluidthrough said second check valve,

(e) an atomizing gas supply pipe surrounding said liquid-fuel-supplytube and said purging-steam-supply conduit and terminating at its outerend in an orifice adjacent to said liquid-fuel-supply tube orifice.

(f) means connecting said liquid-fuel-supply tube and saidpurging-steam-supply conduit so that said tube and conduit move as aunit with respect to the gas supply pipe and in response to variationsin the pressure of the atomizing gas,

(g) means to intermittently supply liquid fuel to saidliquid-fuel-supply tube for ejection through the tube orifice therein,

(b) means to supply 'atomizing gas to said atomizinggas-supply pipe, and

(i) means to supply purging steam to said purgingsteam-supply conduitfor rejection through the tube orifice in said liquid-fuel-supply tubeduring periods when liquid fuel is not being ejected therethrough.

4. The liquid-gaseous fuel burner of claim 3 wherein expansion means areincorporated in said purging-steamsupply conduit.

5. A liquid fuel burner adapted for intermittent operation in a furnacecomprising:

(a) a liquid-fuel-supply tube terminating at its outer end in arestricted orifice,

(b) a first check valve in said liquid-fuel-supply tube located to therear of and closely adjacent to said tube orifice and arranged to permitforward flow of liquid fuel through said supply tube and check valve andout of said tube orifice and to prevent back flow of fluid through saidfirst check valve,

(c) 'a purging-medium-supply conduit communicating with saidliquid-fuel-supply tube between said tube orifice and said first checkvalve,

(d) a second check valve in said purging-mediumsupply conduit oloselyadjacent to said tube orifice and arnanged to permit forward flow ofpurging medium through said purging-medium-supply conduit and escondcheck valve and out of said tube orifice and to prevent back flow offluid through said second check valve,

(e) means to intermittently supply liquid fuel to saidliquid-fuel-supply tube under pressure greater than atmospheric forejection through the tube orifice therein, and

(f) means to continually supply purging medium to saidpurging-medium-supply conduit under pressure greater than atmosphericbut less than that under which liquid fuel is supplied to saidliquid-fuel-supply pipe for ejection through the tube orifice in saidliquid-fuel-supply tube during periods when liquid fuel is not beingejected therethrough.

References Cited by the Examiner UNITED STATES PATENTS 1,587,529 6/26Hoyt 239112 1,841,698 1/32 Barber 158-11 2,818,110 12/57 Rulseh 158-361,953,248 9/60 Troland 239--112 X 3,043,366 7/62 Wentworth 158-36 JAMESW. WESTHAVER, Primary Examiner, MEYER PERLIN, Examiner,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,213,918 October 26, 1965 Eugene M, Rudzki et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 4, line 14, for "0 014 read 0 104 column 6, line 12, for"rejection" read ejection line 35, for "escond" read second Signed andsealed this 31st day of May 1966c (SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Arresting Officer Commissioner ofPatents

1. A LIQUID FUEL BURNER ADAPTED FOR INTERMITTENT OPERATION IN A FURNACECOMPRISING, WITHIN SAID BURNER: (A) A LIQUID-FUEL-SUPPLY TUBETERMINATING AT ITS OUTER END IN A RESTRICTED ORIFICE, (B) A FIRST CHECKVALVE IN SAID LIQUID-FUEL-SUPPLY TUBE LOCATED TO THE REAR OF AND CLOSELYADJACENT TO SAID TUVE ORIFICE AND ARRANGED TO PERMIT FORWARD FLOW OFLIQUID FUEL THROUGH SAID SUPPLY TUBE AND CHECK VALVE AND OUT OF SAIDTUBE OF ORIFICE AND TO PRVENT BACK FLOW OF FLUID THROUGH SAID FIRSTCHECK VALVE, (C) A PURGING-MEDIUM-SUPPLY CONDUIT COMMUNICATING WITH SAIDLIQUID-FUEL-SUPPLY TUBE BETWEEN SAID TUBE ORIFICE AND SAID FIRST CHECKVALVE, (D) A SECOND CHECK VALVE IN SAID PURGING-MEDIUMSUPPLY CONDUITCLOSELY ADJACENT TO SADI TUBE ORIFICE AND ARRANGED TO PERMIT FORWARDFLOW OF PURGING MEDIUM THROUGH SAID PURGING-MEDIUM-SUPPLY CONDUIT ANDSECON D CHECK VALVE AND OUT OF SAID TUBE ORIFICE AND TO PREVENT BACKFLOW OF FLUID THROUGH SAID SECOND CHECK VALVE, (E) A PIPE SURROUNDINGSAID LIQUID-FUEL-SUPPLY TUBE, SAID FIRST CHECK VALVE, SAIDPURGING-MEDIUM-SUPPLY CONDUIT, AND SAID SECOND CHECK VALVE, (F) MEANS TOINTERMITTENTLY SUPPLY LIQUID FUEL TO SAID LIQUID-FUEL-SUPPLY TUBE FOREJECTION THROUGH THE TUBE ORIFICE THEREIN, AND (G) MEANS TO SUPPLYPURGING MEDIUM TO SAID PURGINGMEDIUM-SUPPLY CONDUIT FOR EJECTION THROUGHTHE TUBE ORIFICE IN SAID LIQUID-FUEL-SUPPLY TUBE DURING PERIOD WHENLIQUID FUEL IS NOT BEING EJECTED THERETHROUGH.